126 research outputs found
A Concept for Extending the Applicability of Constraint-Induced Movement Therapy through Motor Cortex Activity Feedback Using a Neural Prosthesis
This paper describes a concept for the extension of constraint-induced movement therapy (CIMT) through the use of feedback of primary motor cortex activity. CIMT requires residual movement to act as a source of feedback to the patient, thus preventing its application to those with no perceptible movement. It is proposed in this paper that it is possible to provide feedback of the motor cortex effort to the patient by measurement with near infrared spectroscopy (NIRS). Significant changes in such effort may be used to drive rehabilitative robotic actuators, for example. This may provide a possible avenue for extending CIMT to patients hitherto excluded as a result of severity of condition. In support of such a paradigm, this paper details the current status of CIMT and related attempts to extend rehabilitation therapy through the application of technology. An introduction to the relevant haemodynamics is given including a description of the basic technology behind a suitable NIRS system. An illustration of the proposed therapy is described using a simple NIRS system driving a robotic arm during simple upper-limb unilateral isometric contraction exercises with healthy subjects
A novel co-locational and concurrent fNIRS/EEG measurement system: design and initial results.
We describe here the design, set-up and first time
classification results of a novel co-locational functional Near-
Infrared Spectroscopy/Electroencephalography (fNIRS/EEG)
recording device suitable for brain computer interfacing applications
using neural-hemodynamic signals. Our dual-modality
system recorded both hemodynamic and electrical activity at
seven sites over the motor cortex during an overt finger-tapping
task. Data was collected from two subjects and classified offline
using Linear Discriminant Analysis (LDA) and Leave-One-Out
Cross-Validation (LOOCV). Classification of fNIRS features,
EEG features and a combination of fNIRS/EEG features were
performed separately. Results illustrate that classification of the
combined fNIRS/EEG feature space offered average improved
performance over classification of either feature space alone.
The complementary nature of the physiological origin of the
dual measurements offer a unique and information rich signal
for a small measurement area of cortex. We feel this technology
may be particularly useful in the design of BCI devices for the
augmentation of neurorehabilitation therapy
A 12-Channel, real-time near-infrared spectroscopy instrument for brain-computer interface applications
A continuous wave near-infrared spectroscopy (NIRS) instrument for brain-computer interface (BCI) applications is presented. In the literature, experiments have been carried out on subjects with such motor degenerative diseases as amyotrophic lateral sclerosis, which have demonstrated the suitability of NIRS to access intentional functional activity, which could be used in a BCI as a communication aid. Specifically, a real-time, multiple channel NIRS tool is needed to realise access to even a few different mental states, for reasonable baud rates. The 12-channel instrument described here has a spatial resolution of 30mm, employing a flexible software demodulation scheme. Temporal resolution of ~100ms is maintained since typical topographic imaging is not needed, since we are only interested in exploiting the vascular response for BCI control. A simple experiment demonstrates the ability of the system to report on haemodynamics during single trial mental arithmetic tasks. Multiple trial averaging is not required
Triple wavelength LED driver for optical brainâcomputer interfaces
A dedicated triple wavelength LED driver is presented for optical
brainâcomputer interfacing (BCI). The solution caters for the constraints
of a common-anode grounded case and modulation up to
several kilohertz that allows source separation of light that has backscattered
from the brain. With total harmonic distortion of 0.95% and
a frequency range of ~40 kHz, the driver has application in a continuous
wave optical BCI. Other modulation strategies such as time division
multiplexing (TDM) are catered for, owing to input DC
coupling. Linearity in the optical output is maintained by the âload
sensingâ differential op-amp on the LEDâs current limiting resistor,
which is the basis for the V-I conversion
Down-Conditioning of Soleus Reflex Activity using Mechanical Stimuli and EMG Biofeedback
Spasticity is a common syndrome caused by various brain and neural injuries, which can severely impair walking ability and functional independence. To improve functional independence, conditioning protocols are available aimed at reducing spasticity by facilitating spinal neuroplasticity. This down-conditioning can be performed using different types of stimuli, electrical or mechanical, and reflex activity measures, EMG or impedance, used as biofeedback variable. Still, current results on effectiveness of these conditioning protocols are incomplete, making comparisons difficult. We aimed to show the within-session task- dependent and across-session long-term adaptation of a conditioning protocol based on mechanical stimuli and EMG biofeedback. However, in contrast to literature, preliminary results show that subjects were unable to successfully obtain task-dependent modulation of their soleus short-latency stretch reflex magnitude
An exploration of EEG features during recovery following stroke â implications for BCI-mediated neurorehabilitation therapy
Background: Brain-Computer Interfaces (BCI) can potentially be used to aid in the recovery of lost motor control in a
limb following stroke. BCIs are typically used by subjects with no damage to the brain therefore relatively little is
known about the technical requirements for the design of a rehabilitative BCI for stroke.
Methods: 32-channel electroencephalogram (EEG) was recorded during a finger-tapping task from 10 healthy
subjects for one session and 5 stroke patients for two sessions approximately 6 months apart. An off-line BCI design
based on Filter Bank Common Spatial Patterns (FBCSP) was implemented to test and compare the efficacy and
accuracy of training a rehabilitative BCI with both stroke-affected and healthy data.
Results: Stroke-affected EEG datasets have lower 10-fold cross validation results than healthy EEG datasets. When
training a BCI with healthy EEG, average classification accuracy of stroke-affected EEG is lower than the average for
healthy EEG. Classification accuracy of the late session stroke EEG is improved by training the BCI on the
corresponding early stroke EEG dataset.
Conclusions: This exploratory study illustrates that stroke and the accompanying neuroplastic changes associated
with the recovery process can cause significant inter-subject changes in the EEG features suitable for mapping as part
of a neurofeedback therapy, even when individuals have scored largely similar with conventional behavioural
measures. It appears such measures can mask this individual variability in cortical reorganization. Consequently we
believe motor retraining BCI should initially be tailored to individual patients
Development of A Versatile Multichannel CWNIRS Instrument for Optical Brain-Computer Interface Applications
This thesis describes the design, development, and implementation of a versatile multichannel continuous-wave near-infrared spectroscopy (CWNIRS) instrument for brain-computer interface (BCI) applications. Specifically, it was of interest to assess what gains could be achieved by using a multichannel device compared to the single channel device implemented by Coyle in 2004. Moreover, the multichannel approach allows for the assessment of localisation of functional tasks in the cerebral cortex, and can identify lateralisation of haemodynamic responses to motor events. The approach taken to extend single channel to multichannel was based on a software-controlled interface. This interface allowed flexibility in the control of individual optodes including their synchronisation and modulation (AM, TDM, CDMA). Furthermore, an LED driver was developed for custom-made triple-wavelength LEDs. The system was commissioned using a series of experiments to verify the performance of individual components in the system. The system was then used to carry out a set of functional studies including motor imagery and cognitive tasks. The experimental protocols based on motor imagery and overt motor tasks were verified by comparison with fMRI. The multichannel approach identified stroke rehabilitation as a new application area for optical BCI. In addition, concentration changes in deoxyhaemoglobin were identified as being a more localised indicator of functional activity, which is important for effective BCI design. An assessment was made on the effect of the duration of the stimulus period on the haemodynamic signals. This demonstrated the possible benefits of using a shorter stimulus period to reduce the adverse affects of low blood pressure oscillations.
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